Add water to the instant pot. Place the green beans on a trivet. Start the instant pot on Steam mode for 0 minutes on high pressure. When the instant pot beeps, quickly release the pressure manually. Remove the steamer basket carefully as it is hot. Discard water.
Place the steel insert back in the pot and heat it on Sauté mode. Add butter & let it melt. Add garlic & sauté for a few seconds until it is lightly golden brown. Add the steamed green beans and gently stir. Cook for a couple of minutes while stirring frequently.
Add lemon juice. Season with salt and pepper.